Is 183000 miles too many for 1998 Frontier? Four cylinder, 4x4 5 speed?

No amount of miles is too many if you take care of the vehicle.

Let me elaborate on Justin's answer ... The truck has 183,000 miles and is 14 years old. If you accept that "average" mileage is 12,000 miles per year then this truck has mileage slightly higher than average. If you believe ( as I do ) that "average" mileage is more like 15,000 per year then this truck has slightly lower mileage than average. More important than the number of miles on the odometer however is, the type of mileage ( highway or stop and go ), how the vehicle was driven ( like a "hotrod", or like a pick up truck ) and how well it was maintained. Not saying that this is a tell-all sign of how the vehicle was maintained or treated but, it's definitely a few signs to look for ... look for debris ( rocks, grass, twigs etc. ) where it shouldn't be unless the truck was used hard off road such as on top of skid plates, inside of frame rails and on top of axles. Also look for damage to axles or skid plates from scraping rocks, etc. Check the inside of the oil fill cap and inside the valve cover does it look reasonably clean ? If it does, it probably had regular oil changes. If it's caked with sludge, it probably did not. Of course there's alot more to consider that I won't get into here but, as Jason said, very low mileage with poor treatment and care is by far much worse than very high mileage with meticulous care and mature, adult treatment.